Surry and Randolph counties are now among nine North Carolina counties in the investigation, SBI officials said Wednesday.

Surry County deputies said they forwarded to the SBI a report of a student seeing a nude photo through the Instagram app. Deputies said they weren't able to find the evidence, as the page was already taken down.

Search warrants show authorities have subpoenaed Facebook, which owns Instagram, for user information associated with several accounts. SBI officials said they've identified more than 30 accounts as potential violators.

The SBI investigation began earlier this month when a woman called Wake Forest police to tell them that her daughter had learned that someone had posted nude photos of her on Twitter and Instagram. SBI officials later said they were investigating reports by students from at least a half dozen Wake County high schools.

Two girls ages 14 and 17 then told Durham County deputies they saw nude photos of themselves being shared on Instagram.

Other counties in the expanded investigation include Chatham, Craven, Edgecombe, Johnston and Pitt.